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b2441318 | 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
0f8f2aaa WL |
2 | #ifndef __LINUX_LOCKREF_H |
3 | #define __LINUX_LOCKREF_H | |
4 | ||
5 | /* | |
6 | * Locked reference counts. | |
7 | * | |
8 | * These are different from just plain atomic refcounts in that they | |
9 | * are atomic with respect to the spinlock that goes with them. In | |
10 | * particular, there can be implementations that don't actually get | |
11 | * the spinlock for the common decrement/increment operations, but they | |
12 | * still have to check that the operation is done semantically as if | |
13 | * the spinlock had been taken (using a cmpxchg operation that covers | |
14 | * both the lock and the count word, or using memory transactions, for | |
15 | * example). | |
16 | */ | |
17 | ||
18 | #include <linux/spinlock.h> | |
57f4257e PZ |
19 | #include <generated/bounds.h> |
20 | ||
21 | #define USE_CMPXCHG_LOCKREF \ | |
22 | (IS_ENABLED(CONFIG_ARCH_USE_CMPXCHG_LOCKREF) && \ | |
597d795a | 23 | IS_ENABLED(CONFIG_SMP) && SPINLOCK_SIZE <= 4) |
0f8f2aaa WL |
24 | |
25 | struct lockref { | |
bc08b449 | 26 | union { |
57f4257e | 27 | #if USE_CMPXCHG_LOCKREF |
bc08b449 LT |
28 | aligned_u64 lock_count; |
29 | #endif | |
30 | struct { | |
31 | spinlock_t lock; | |
360f5479 | 32 | int count; |
bc08b449 LT |
33 | }; |
34 | }; | |
0f8f2aaa WL |
35 | }; |
36 | ||
2f4f12e5 | 37 | extern void lockref_get(struct lockref *); |
360f5479 | 38 | extern int lockref_put_return(struct lockref *); |
2f4f12e5 | 39 | extern int lockref_get_not_zero(struct lockref *); |
450b1f6f | 40 | extern int lockref_put_not_zero(struct lockref *); |
2f4f12e5 LT |
41 | extern int lockref_get_or_lock(struct lockref *); |
42 | extern int lockref_put_or_lock(struct lockref *); | |
0f8f2aaa | 43 | |
e7d33bb5 LT |
44 | extern void lockref_mark_dead(struct lockref *); |
45 | extern int lockref_get_not_dead(struct lockref *); | |
46 | ||
e66cf161 | 47 | /* Must be called under spinlock for reliable results */ |
11209f3c | 48 | static inline bool __lockref_is_dead(const struct lockref *l) |
e66cf161 SW |
49 | { |
50 | return ((int)l->count < 0); | |
51 | } | |
52 | ||
0f8f2aaa | 53 | #endif /* __LINUX_LOCKREF_H */ |